1. Technical Field
The present disclosure relates to the joining of materials and more particularly to joining materials such as ceramic matrix composites and refractory metals.
2. Background Information
Ceramic matrix composites are a type (CMC) of composite material and include ceramic fibers embedded in a ceramic matrix. While ceramics on their own are brittle, cracking easily, ceramic matrix composites are durable and have a high crack resistance. They are useful in situation in fields requiring high-temperature durability and resistance to corrosion. Refractory metals are a class of metals that are resistant to heat and wear. Like ceramic matrix composites, they are durable at high-temperatures.
Because ceramic matrix composites and refractory metals melt at high temperature, pieces are often joined using brazing. In brazing, a joining material is melted and flows between pieces, where it hardens, joining the pieces. Such joining procedures are typically carried out in either a large furnace, or in an open environment. In a furnace, the entire piece may be heated in a vacuum or inert atmosphere to melt the brazing material. In an open environment, the piece may be heated locally at the spot to be joined. This local heating allows the piece to be heated and cooled quickly, and allows brazing of pieces that are too large for a furnace or may be damaged by furnace heating of the entire piece. While local heating is effective, many joining materials react with oxygen and/or nitrogen, so it is beneficial if the piece is heated and cooled as quickly as possible to deter the joining materials from reacting with oxygen and/or nitrogen. In some instances, the local heating of a piece may be done through the use of a laser. The laser is able to direct a precise beam to heat the piece at a precise location.
To inhibit the either the piece or the filler material from reacting with oxygen or nitrogen, ambient gas may be shielded from the piece. For example, a shielding gas may be directed to the piece as it is heated to inhibit reaction with the ambient air. Or the piece and the heat source may be placed in a sealed environment where the piece may be heated in a controlled environment.
Each of these techniques for joining materials have potential downsides. Heating and cooling the piece quickly allows the joint to react with the ambient air, even if only momentarily. Similarly, while shielding gas may inhibit reaction of the ambient air with the piece or the filler, some reaction may still take place. Heating the piece in a controlled environment may suitably inhibit the reaction with ambient air, but a sealed environment large enough to house the pieces being joined and the heat source is typically very expensive.